DLT tapes

Information about DLT tapes and drives

POLDER standard products are archived:

• on DLT (Digital Linear Tape) tapes in case of voluminous products (level 1 products and level 2 directional products for land surfaces and ocean colour thematics),
• on CD-ROMs in case of low volume products (all other POLDER products).

The Digital Linear Tape technology has been developed by Digital Equipment Corporation (DEC) since 1985. Early 1995, this activity was transferred to another company, QUANTUM, which goes on with the development of DLT products.

The DLT technology offers a better combination of storage capacity, transfer rate, reliability (durability and data integrity) and price than helical scan tape technology used by Exabyte (8mm tapes) or DAT (4 mm tapes) tape drives.

The POLDER production center uses DLT 2000 tape drives which deliver compactapes 3 (also called DLTtape III).
These tapes can be read on following DLT drive models: 2000, 2000 XT, 4000, 7000, 4500, 4700, 2700XT, 2500XT, DLTsto.
DLT 2000 tape drive features a 1.25 megabytes per second native sustained transfer rate with a native storage capacity of 10 gigabytes (GB) per cartridge. Add data compression and you can boost capacity up to 20 GB (depending on the content of data) with a transfer rate of 2.5 megabytes (MB) per second.

If you are a new POLDER data user and if you want to purchase a DLT drive, please note hat DLT 2000 are no more available, they are replaced by DLT 2000 XT.
DLT 2000 XT tape drives features a 1.25 megabytes per second native sustained transfer rate with a native storage capacity of 15 gigabytes (GB) per cartridge using compactapes 3 XT (also called DLTtape III XT) and with data compression up to 30 gigabytes (GB) per cartridge with a transfer rate of 2.5 megabytes (MB) per second. Concerning POLDER standard products, the average compression rate that can be obtained is 1.2, that leads to a storage capacity of 12 gigabytes (GB) per cartridge in case of compactapes 3 (also called DLTtape III).

For example, in POLDER data archive, one tape contains:

• one day of POLDER level 1 products, i.e. 14 to 5 products of 742 megabytes each per tape,
• one week of POLDER level 2 directional products for land surfaces thematic, i.e. 100 products of 36 megabytes each per tape,
• one week of POLDER level 2 directional products for ocean colour thematic, i.e. 100 products of 75 megabytes each per tape.

If you need more technical information, or if you want to know where to buy DLT products, please, go to: http://www.quantum.com/products/dlt.